Here's a pic. Since I took it he's gotten even bigger. He's got 3 tsp epsom salts per gallon in his tank, and I've been feeding him more lightly than usual (teeny pinch of dried daphnia, or a pellet or two of Hikari Betta Gold) once a day, and I skip feeding him at all every couple of days. How long will this take to resolve? (It's been several weeks now that I've been doing epsom salts and daphnia.) Is there something more I can do? Is it possible this could kill him?

Housing
What size is your tank? 2.5 gallons
What temperature is your tank? 80 degrees F
Does your tank have a filter?yes
Does your tank have an air stone or other type of aeration?no
Is your tank heated?yes
What tank mates does your betta fish live with?java ferns, teeny snails

Food
What type of food do you feed your betta fish? Hikari Betta Gold, dried daphnia
How often do you feed your betta fish?2x/day, 1 or 2 pellets at a time

Water Parameters:Have you tested your water? If so, what are the following parameters?

Ammonia: 0Nitrite:0Nitrate:0pH:7.5Hardness:dunnoAlkalinitydunno:

Symptoms and Treatment
How has your betta fish's appearance changed? BIG Belly
How has your betta fish's behavior changed? More sluggish than usual
When did you start noticing the symptoms? Big belly started creeping up maybe a month or two ago, it took us a while to realize what was going on.
Have you started treating your fish? If so, how?3 tsp epsom salts per gallon, daphnia
Does your fish have any history of being ill? no
How old is your fish (approximately)? We've had him two years this MayMaintenance
How often do you perform a water change? 2x/week
What percentage of the water do you change when you perform a water change?50%/75%
What type of additives do you add to the water when you perform a water change?
Nutra-Fin

Stop feeding him completely for a few days maybe even a week. He won't starve and if you keep giving him food he may never be able to clear his system. Another thought is he could be eating the little snails. A large apple or mystery snail can be an ok tank mate (but not in that size container) but little snails aren't generally good because bettas may eat them - most I've seen do. Snails are also very dirty and muck up the water quickly and aren't generally a good idea in small tanks. I had one coexist with a tiny snail ok but I think I was just plain lucky because it was my first betta and I didn't really know what I was doing and it just happened to hitch a ride on a plant from the LFS, and in my infinite wisdom thought "hey, cool, free snail!" and it just worked.

What does his poop look like? Have you seen any in the last week?

It looks like your water is good and your water changing habits are good.

I would switch pellets. Hikari used to make one of the best pellets but they've switched their ingredients and now it's just mostly full of wheat and other fillers. They tend to lead to constipation because of how much they swell. I would look for Omega One Betta Buffet (You can feed 2-4 like the Hikari) or New Life Spectrum Betta, which is my personal favorite. You can feed more like 5-8 split up into two or even three small meals because they're a lot smaller. I really like the NLS because they're the highest in protein, smaller, don't swell at all (in fact they're sink pretty quick if your guy isn't right on it) and have the fewest fillers.

Feeding freeze dried daphnia is alright but you need to thoroughly soak it in a little cup with some tank/dechlorinated water before feeding because it will also absorb a lot of moisture and freeze dried foods can also lead to constipation unless you soak, but daphnia is generally ok to feed occasionally to help regulate or during this problem.

Sooo.. I would

* Continue epsoms
* Give him a break from all food for a few days or even a week - until you see a lot of poop pass - then report back on what the poop looks like
* Switch pellets and soak any freeze dried food you supplements
* Try to remove the snails
* Be prepared that if his poo is white, clear, stringy or segmented he may need some meds. Look for Kanaplex by Seachem or Maracyn Plus as they can be hard to find but are the most effective on internal bacterial infections - which tends to happen with chronic long term constipation.

Give him 1/4 of a pea, fast him for up to a week, then get him on to better foods. Yes, they can die from being constipated, but it is usually from complications like starvation or infections. Mine died in the summer after a two month (that's right,two months) battle with severe constipation.
Good luck!

If you choose to feed a pea you need to use fresh or frozen. The pea should be placed in a small microwaveable cup or dish of some kind that has never seen soap or chems. Nuke it for 10 seconds. At this point the shell should be easy to strip off (or sometimes they explode out of their shell in this time). You should see two halves inside the shell. You can break up as much as one half of it and fit a bit at a time or as little of 1/4 (half of one of the halves).

Peas are not generally suggested here and definitely should not be fed very often because they are hard on the digestive tract. You will see him poop it completely undigested.

Thank you Callistra for the excellent plan! I had been wondering if it could be his food, I'll try the new food after fishy fasts for a couple of days. I also had been feeling as if I was missing something important just dumping the dried daphnia in his tank- I do remember that I needed to soak dried food for the fancy goldfish I had ages ago, but goldfish are so inbred and so prone to swim bladder problems I didn't realize I might have to do it for other fish too.

I haven't seen him poop for a long time. Last time I did it was like a little fat brown "C" but that was a long time ago. I'll keep an eye out for it.

I'll keep the pea in mind, but it sounds as if it'd be worthwhile to let him fast and then try the other foods first.

Progress report on poor fishy- if anything, he's gotten worse. His whole body looks misshapen. There's been no poop that I know of. He acts like he's starving and begs and begs for food when I change his water. It's been at least three days since I fed him. Here's a pic of the poor guy...

You can see fluid build up. It's more than constipation. When you see fluid like that and it grows despite not feeding, it's time for a good internal antibiotic now. Be looking for Kanaplex by Seachem or Maracyn Plus (not to be confused with Maracyn or Maracyn II).

So he's been on 3 tsp per Gallon epsoms since the 27th? So that means in his 2.5g you're putting 7.5 tsp of epsoms? Continue this. I'd be doing 100% water changes every other day too, along with the redosing of meds and epsoms. I expect this to take 2 weeks to complete, but you should start seeing some good results in a few days..